Gas turbines generally include a turbine rotor (wheel) with a number of circumferentially spaced buckets (blades). The buckets generally may include an airfoil, a platform, a shank, a dovetail, and other elements. The dovetail of each bucket is positioned within the turbine rotor and secured therein. The airfoils project into the hot gas path so as to convert the kinetic energy of the gas into rotational mechanical energy. A number of cooling medium passages may extend radially through the bucket to direct an inward and/or an outward flow of the cooling medium therethrough.
Leaks may develop in the coolant supply circuit based upon a gap between the tabs of the dovetails and the surface of the rotor due to increases in thermal and/or centrifugal loads. Air losses from the bucket supply circuit into the wheel space may be significant with respect to blade cooling medium flow requirements. Moreover, the air may be extracted from later compressor stages such that the penalty on energy output and overall efficiency may be significant during engine operation.
Efforts have been made to limit this leak. For example, one method involves depositing aluminum on a dovetail tab so as to fill the gap at least partially. Specifically, a 360-degree ring may be pressed against the forward side of the dovetail face. Although this design seals well and is durable, the design cannot be easily disassembled and replaced in the field. Rather, these rings may only be disassembled when the entire rotor is disassembled.
There is thus a desire for improved dovetail tab sealing systems and methods. Such systems and methods should adequately prevent leakage therethrough so as to increase overall system efficiency while being installable and/or repairable in the field.